A number of known swimming pool cleaning devices comprise:                a hollow body and members for guiding and driving the body over the immersed surface in a main direction of advance, called the longitudinal direction,        a filtration chamber which is provided in the hollow body and which has:        at least one liquid inlet into the hollow body located at the base of the hollow body,        at least one liquid outlet out of the hollow body,        a hydraulic circuit which is capable of providing a flow of liquid between each inlet and each outlet through a filtering device which is mounted in the filtration chamber, under the action of a pumping device.        
In these known devices, a flap for access to the filtering device must be provided in order to allow it to be removed for the purpose of cleaning it. In prior devices (U.S. Pat. No. 6,013,178), the flap for access to the filtration device is generally located at the base of the hollow body, the liquid inlets being necessarily provided with non-return devices, such as valves. This arrangement is not convenient for the user who must invert the device beforehand which may damage it and also bring about undesirable untimely occurrences of flow. Otherwise, if the access flap is arranged at the top of the device, the hydraulic circuit must have a particularly complex path (cf., for example, U.S. Pat. No. 6,409,916) which requires the use of high-power pumping devices, thus bringing about significant energy consumption.
Furthermore, in all of the known devices, the unclean circuit, that is to say, the portion of the hydraulic circuit of the device which conveys the liquid which has not yet been filtered by the filtering device and which may comprise debris, is not readily accessible for the user. In particular, in some devices (U.S. Pat. No. 6,409,916), access to this unclean circuit may require that the device be disassembled which can be carried out only by a specialist technician in particular so as not to invalidate any manufacturers warranty for the device. In other devices, the access to this unclean circuit also requires the device be inverted.
As a result, the unclean circuits of the known devices are practically never completely cleaned. Consequently, these devices do not have filtration performance levels which are stable over time, in particular when surfaces which are heavily clogged with debris are cleaned. Furthermore, the service periods of the device between which a cleaning operation must be carried out are relatively short if the surface is very clogged with debris and in particular very variable depending on the type of waste recovered with the result that they vary randomly for the user. For example, if the pool is clean but the device draws in a single large leaf, this leaf is capable of substantially blocking the filtering device, making it necessary to clean the filtering device. In this manner, the filtration and suction performance levels of these known devices may decrease rapidly in a random manner from the viewpoint of the user and when the quantity of debris recovered is very much lower than the quantity corresponding to the capacity of the filtering device. However, the performance levels of the device, regardless of the frequency with which the filtering device is cleaned, are never equivalent to the initial cleaning performance levels, since the unclean circuit of the device is never completely cleaned.
Furthermore, the operations for removing and cleaning the filtering devices are unclean, unpleasant and may make the device and/or the user and/or the swimming pool dirty.